Truly a sad story! Why? Why did that guy feel he had to do this? It is something I will never understand.
Bad guys get off on doing bad things. Bad guys do bad things because they expect to get away with doing bad things. The (alleged) perp in this case has a history of doing bad things, and was still walking the streets a free man. He apparently had a reasonable expectation of getting away with doing the bad things he gets off on doing.
Revenge possibly, or maybe it was just anger at whitey for him being in prison for 20+ years..................